We always stay at DLP but visit Paris for 2 or 3 days. It's very easy to get to Paris from Disney, around 45mins on the train.
We usually stay at one of the Disney partner hotels such as Magic Circus or Dream Castle. You can usually get good B&B or room only deals for these on Expedia, Alpha rooms or Travel republic, then just buy tickets (or an annual pass) for your Disney days.
Busses run from the partner hotels to the train station around every 20mins.
If you get a mobilis ticket for the train you can get a return trip into Paris and unlimited use of the Paris Metro for the day for around 16 each. It's really easy to find your way to all the sights around Paris using the Metro, and much cheaper than a tour.
